In various stages in the manufacture of substrates, such as printed circuit boards, it is necessary to locate each substrate in a processing apparatus to a high degree of accuracy. For example, in the assembling of electronic components having projecting leads to a printed circuit board, by inserting leads of the components through preformed apertures in the board, the board generally is positioned on an X-Y support table in an automatic component-insertion apparatus. The X-Y support table then is indexed to present successive sets of lead-receiving apertures in the board beneath an insertion head for the automatic insertion of the component leads into apertures of the board. With the advent of miniaturized electronic components and high density circuit patterns on printed circuit boards, it is essential that each printed circuit board be located on the X-Y support table of the component-insertion apparatus so as to be aligned with respect to a component-insertion head to on the order of within .+-.0.005 inch. It also is desirable that the board alignment arrangement utilized be readily compatible with the automatic feeding of the boards into the component-insertion apparatus and the subsequent automatic discharge of the boards from the apparatus.
A known method of locating the printed circuit boards in the component insertion apparatus involves forming locating holes in the printed circuit boards by drilling or punching holes in a substrate blank from which a plurality of the boards are formed. Subsequently, each board is positioned in the component-insertion apparatus and locating dowels are advanced through the locating holes in the board to align the board with respect to the component-insertion head. Where the boards are to be fed into the component-insertion apparatus automatically, this normally requires that the locating dowels be retracted for the feeding of one of the boards into the apparatus into an approximate desired location in the apparatus. The locating dowels then are advanced through the locating holes in the board to align the board with respect to the component-insertion head. A disadvantage of this arrangement is that dowel-carrying arms and a mechanism for advancing and retracting the dowels may interfere with the insertion of certain components into the board, requiring that these components subsequently be inserted by hand.
Accordingly, another method of locating the printed circuit boards in the component-insertion apparatus involves the use of locating members which are receivable in locating recesses formed in one or more edges of each printed circuit board by punching. For example, a known technique utilizes a V-shaped locating member or a circular dowel receivable in a locating recess in the shape of a V-shaped notch in one edge of the printed circuit board, to locate the board in X and Y directions. Since punching can be inaccurate to on the order of .+-.0.015 inch, however, a second locating recess which receives another locating member, such as a second circular dowel, for locating the board in the Y direction, is provided in the one edge of the board in the shape of an elongated slot to compensate for the recess-forming tolerance error in the X-direction.
Another known printed circuit board edge-locating method utilizes punch-formed V-shaped notches at opposite ends of each printed circuit board. In use, the board is positioned in a processing apparatus so that one of the V-shaped notches receives a fixed locating pin. A retractable locating pin then is advanced by an air cylinder into the other V-shaped notch to align the printed circuit board in the apparatus.
In a similar locating method, the locating members are spring-loaded and of a V-shaped configuration. In addition, a third spring-loaded V-shaped locating member is receivable in a third V-shaped notch in a side edge of the printed circuit board intermediate its opposite ends. The use of circular dowels on a conveyor, which are receivable in respective ones of a pair of V-shaped notches in one end of a printed circuit board, for aligning the circuit board as the board is fed to a processing apparatus, also is known.
Since the above-described edge-locating arrangements utilize V-shaped edge-locating recesses formed by the relatively inaccurate process of punching, these arrangements are not particularly suited for the assembling of miniaturized components on high circuit density printed circuit boards, in which extremely accurate board alignment is required. Further, for various reasons, these arrangements are not readily adaptable to the automatic feeding of the printed circuit boards into and out of a processing apparatus. Accordingly, a primary purpose of this invention is to provide new and improved methods of accurately locating substrates, such as printed circuit boards, in associated processing apparatus.